Objective: This study focused on the effects of changes to patient medication regimens, adverse drug reactions, abnormal laboratory results during hospital stay, and discharge diagnosis on unplanned readmission rates of elderly patients with cardiovascular disease. The objective of the study was to identify which variables predict non-elective hospital readmission.
Design: A retrospective cohort design was used with random review of medical charts of patients admitted to the study-site hospital over a 6-month period.
Setting: Antrim Area Hospital, a 385-bed hospital located in a rural setting.
Patients: 100 elderly cardiology patients (47 male, 53 female, average age 75 ± 6 years) with a non-elective admission to the study-site hospital.
Main Outcome Measures: Non-elective readmission rates to the study-site hospital during the 12 months after discharge.
Results: An unplanned readmission rate of 32% 1 year post hospital discharge was noted, with mean length of time to first readmission of 40.7 days. Chi-squared analysis revealed statistically significant relationships between patients being readmitted one or more times within a 12-month period and the following variables: acute coronary insufficiency as a primary diagnosis (p = 0.009, odds ratio = 0.32), patients discharged on a calcium-channel blocker (p = 0.023, odds ratio = 3.18), one or more changes in strength/dose of drugs during hospital stay (p = 0.028, odds ratio = 0.38), and patient discharged on a potassium-channel activator (p = 0.034, odds ratio = 2.72). Multivariate logistic regression analysis produced a five-variable model predictive of hospital readmissions with a specificity of 84.1%, sensitivity of 61.3% and accuracy of 77.0%.
Conclusion: The present research highlights a number of risk factors that are associated with multiple hospital admissions of elderly patients with cardiovascular disease. This knowledge should be of use to medical staff when identifying patients in need of intensive discharge planning.
Patients with cardiovascular disease have been found to have particularly high rates of readmission to hospital. Studies have reported readmission rates of up to 47% within 90 days of discharge. Determination of risk factors for early readmission has focused on selected populations, especially when investigating elderly patients with cardiovascular disease. Chin and Goldman investigated correlates of early hospital readmission or death in patients diagnosed with congestive heart failure (CHF). These researchers prospectively followed 257 patients with non-elective admissions to hospital where CHF was diagnosed. The readmission rate for these patients 60 days post-discharge was 31%. Predictors of readmission or death included single marital status and systolic blood pressure of ≤100mm Hg on admission. It was therefore concluded that both medical and social factors were important contributors to a patient's clinical decline. In a previous study, Vinson et al. also concentrated on elderly patients with CHF. They compared those who were readmitted 90 days post-discharge with those who were not rehospitalised, and concluded that factors predictive of readmission included a prior history of heart failure, four or more readmissions in the previous 8 years, and heart failure precipitated by an acute myocardial infarction or uncontrolled hypertension.
Maynard et al. evaluated patients discharged from hospital having survived an acute myocardial infarction. This retrospective cohort study involved collection of medical, demographic and socioeconomic information on 5051 individuals discharged from hospital over a 2-year period. The readmission rate over a follow-up period of 3 years was determined. Twenty percent of patients were readmitted, with an acute myocardial infarction again being the primary diagnosis, while 54% were readmitted for other cardiovascular events. To determine why these hospital readmissions occurred, stepwise logistic regression was used to identify predictors of rehospitalisation in the year after discharge. History of CHF, history of angina pectoris, female gender, history of hypertension, history of coronary artery bypass surgery and prolonged angina during hospitalisation were found to be associated with increased likelihood of readmission.
Cardiovascular drugs are among the most commonly prescribed medicines in elderly patients. More than 80% of elderly patients have one or more chronic illness, thus it is common for them to be taking several medications. As the number of drugs taken by a patient increases, so too does the risk of adverse drug reactions (ADR) and drug-drug inter-actions. It is interesting to note that none of the aforementioned studies focused on the medication taken by patients, particularly when it is realised that ADR and treatment failure can account for 11.4% of hospital admissions, and that approximately one-quarter of these medication-related problems is associated with cardiovascular drugs. Dartnell et al. found that 5.7% of emergency admissions to hospital over a period of 1 month were drug-related, with 83 drugs being implicated. Over 30% of these medications included antihypertensives, diuretics, anticoagulants and other cardiovascular drugs.
Most research to date has concentrated on ADR and adverse drug events (ADE) resulting in hospital admission, but few examine adverse drug reactions experienced during hospital stay, and the resultant outcomes for such patients, such as length of stay and readmission to hospital. However, one study involving 157 general medical admissions of patients aged over 70 years of age did investigate ADE in hospitalised elderly individuals, with the objective of examining the association between potential risk factors and ADE. The relationships between ADE occurrence, length of hospital stay and functional decline were also investigated. It was found that ADE were associated with the number of new inpatient medications and cognitive status on admission, but not demographic, disease or physical function variables. Patients who experienced an ADE had a significantly longer hospital stay than those who did not (p = 0.022), and they also experienced a decline in one or more activities of daily living.
It would be expected that the older elderly patient would be more vulnerable to ADE. This hypothesis has been researched in a number of studies that have produced unexpected results. In a study of hospitalised patients by Carbonin et al., univariate analysis revealed that the incidence of ADR increased from 3.3% at under age 50 years to 6.5% at age 70 to 79 years, but decreased again to 5.8% in patients aged over 80 years. In an earlier study, Hurwitz and Wade found a similar pattern of results in their study of adverse drug reactions experienced during hospitalisation. Patients aged 70 to 80 years experienced the highest incidence of adverse drug reactions, while those aged over 80 years experienced an incidence comparable to those aged 40 to 50 years. Coltand Shapiro performed retrospective reviews of patient charts (n = 233) to determine the rate of occurrence of drug-induced illness as a reason for unplanned hospital admission. They found that the incidence of ADR was indeed more common in the elderly (over 65 years) than the young (11.6% vs 5.6%), but this difference did not reach statistical significance. They concluded that further research was required to assess the exact role of patient age, and the number and type of medications involved in drug-induced illness.
The aim of this exploratory study was to identify the influence of the following factors during hospitalisation on the readmission rate of elderly patients with cardiovascular disease:
Changes to patient medication regimens
ADR
Abnormal laboratory results
Cardiovascular drugs prescribed
Medical and demographic factors.
Having established any relationship between these factors and an unplanned return to hospital within 1 year, the study also aimed at developing a multivariate model to predict hospital readmissions.